I have been using Manager for several months and suddenly no longer opens. When I click Open I get the do you want to open this because it has been dowloaded from the internet and I choose Open. I am on macOS Sierra version10.12.1. It worked previously.
“does not open” does not give much information.
what exactly happens after you click open?
do you see any error message?
what version of Manager?
read the updated guide Install or update desktop edition on macOS | Manager